The present invention relates generally to an electrostatic spray coating apparatus for electrostatically coating the surface of an object with an atomized liquid paint. More particularly, the invention relates to a rotary head of an electrostatic spray coating apparatus for ejecting an atomized liquid paint toward an object which is to be coated with a paint.
UK Patent Publication No. GB A 2193447 discloses an exemplary electrostatic spay coating apparatus in which a cup-shaped or disk-shaped rotary head having integrated inner and outer cup members is provided for discharging a liquid paint in the form of an annular thin-film from an inner peripheral surface of the inner cup member, and in which an annular slit for leading and ejecting a gas flow for atomizing the liquid paint discharged from the inner peripheral surface of the inner cup member is defined between the inner and outer cup members of the rotary head.
The above-mentioned electrostatic spray coating apparatus, however, has a disadvantage in that the gas flow can be led through the annular slit only in a predetermined direction with respect to the axis of rotation of the rotary head, resulting in a fixation of condition of atomization which are to be adjusted to atomize in an optimum state the liquid paint in accordance with various coating conditions.
In order to adjust the width of an ejection pattern of a liquid paint or the state of atomization of the liquid paint, it has been necessary to change the pressure or speed of ejection of the gas flow. In this case, however, changes in the pressure or speed of ejection of the gas flow tend to cause the state of atomization of the liquid paint to be instable, resulting in a deteriorated quality of a coating film formed on the object surface due to formation of ultrafine particles of liquid paint having non-uniform sizes.